Do you actually mean a separate widget, or are you referring to the 'Manage Print jobs' icon in the KDE System Tray on the Panel?

If you meant the latter, right-click on the System Tray and select 'System Tray Settings'. Click on 'Unlock Widgets' and make sure 'Manage Print Jobs' is ticked. Then it will be displayed in the System Tray when you launch a print job, and only visible (and selectable) by clicking on the System Tray's up-allow otherwise. However, if you want the icon to be visible in the System Tray at all times, click on Entries in the System Tray Settings and change the Visibility of 'Manage Print Jobs' to 'Always Visible' and click 'Apply'._________________~amd64, OpenRC, FGLRX, KDE
Fitzcarraldo's blog

Just to make sure I understand correctly, are you saying that you do have the KDE System Tray but there is no entry for 'Manage Print Jobs' in the 'System Tray Settings', so you are unable to select it using the procedure I mentioned in my previous post?_________________~amd64, OpenRC, FGLRX, KDE
Fitzcarraldo's blog

I begin to understand my problem. With your guidance in your second last post I managed to discover that the "Print jobs" actually is activated in the System Tray. But it is not visible, eventhough I select "Always visible". If I click inbetween the "Notoifications and Jobs" icon and the "Text Snippets" icon the "Print jobs" application pops up. In other words it is there but does not show as an icon. The icon is "blanc"._________________/Phil

But, perhaps before you do that, have you checked that you have Oxygen selected for the widget style and for the icon theme (Kicker > 'System Settings' > 'Application Appearance')? Maybe try a few other themes to see what happens to the icon._________________~amd64, OpenRC, FGLRX, KDE
Fitzcarraldo's blog